Getting a “Could not find permission set named ‘ASP.Net’” error on your TFS 2010 server? It may have to do with the fact you’re trying to run ASP.NET as a child site of a SharePoint Web Site. The problem is described in the “ASP.NET 4 braking changes” site:

This error occurs because the ASP.NET 4 code access security (CAS) infrastructure looks for a permission set named ASP.Net. However, the partial trust configuration file that is referenced by WSS_Minimal does not contain any permission sets with that name.

Currently there is not a version of SharePoint available that is compatible with ASP.NET. As a result, you should not attempt to run an ASP.NET 4 Web site as a child site underneath SharePoint Web sites.

There is a workaround you could try by setting this in your web.config, if you know what you’re doing:

<trust level="Full" originUrl="" />